SEOUL (Reuters) - If South Korean President Park Geun-hye is impeached in parliament on Friday, she faces an uphill court battle to overturn the motion, experts say, even though the judges were all appointed by her and her conservative predecessor.
An impeachment vote appears likely, and the nine-judge Constitutional Court would have up to six months to uphold or overturn it.
Legal experts say the case against the president looks strong, while the overwhelming public mood is for Park to quit, with massive weekly protests calling for her resignation and an approval rating down to just 4 percent.
But the conservative make-up of the Constitutional Court would appear to be in Park's favour. For her to be impeached, at least six of the nine judges must uphold the parliamentary motion.
The terms of two justices are set to expire soon - one on Jan. 31 and the other on March 13 - and experts say it is unlikely that replacements would be appointed amid the political crisis, potentially leaving just seven judges, the minimum required.
A smaller bench works in Park's favour because the number of judges needed to uphold impeachment remains at six.
"Two judges retiring is like two judges voting for overturning," said Chon Jong-ik, a law professor at Seoul National University who served as the court's spokesman during the impeachment trial of President Roh Moo-hyun in 2004.
Roh is the only South Korean president to be impeached, but the Constitutional Court overturned the motion. In that case, impeachment was unpopular with the public, which saw it as an abuse of power by the opposition, which held a parliamentary majority.
However, Ha Kyung-chull, who led Roh's nine-member team of lawyers at the trial, said the case against Park - that she allowed a friend to meddle illegally in government affairs - appears to be strong.
"The argument will be that, as she has said all along, she has acted believing it's all for the national interest and that she did nothing for personal gain, and she believes that will be sufficiently convincing," said Ha, who served on the Constitutional Court from 1999 to 2004 before entering private practice.
But he said there were "clear grounds to support impeachment".
No South Korean president has failed to finish a five-year term under the democratic president set up in 1987.
The Constitutional Court will hear arguments from the two sides - the chair of parliament's Judiciary Committee for the impeachment motion and lawyers representing Park - in open hearings before delivering its ruling.
Park is unlikely to be present.
If she is impeached in parliament, she will have to step down from the presidency and the country's prime minister will serve as interim leader while the court reviews the impeachment.
Political parties have said they believe there were more than the 200 votes needed to impeach Park in the 300-seat parliament on Friday, with support from some members of Park's conservative Saenuri Party.
If passed, the nine judges who work from a court building a few blocks from the presidential Blue House will be making a once-in-a-career decision.
"The minute the impeachment motion is passed by parliament, you can say the judges will promptly lose their appetites," said Kim Jong-dae, who served on the bench between 2006 and 2012.
"The stress will be immense."
The court, set up in 1988, is one of the country's two highest and hears cases involving interpretation of the constitution. The other, the Supreme Court, is the highest court of appeal.
All nine judges are appointed by the president, but three are recommended by the Supreme Court's chief justice and another three by parliament.
The current bench is considered largely conservative, frequently ruling for the government in landmark cases during Park's presidency and that of her predecessor, Lee Myung-bak.
In 2014, in an eight-to-one decision, the court ruled to disband a progressive political party accused of pro-North Korea activities, saying it violated the principles of free democracy by illegally advocating the views of Pyongyang, and stripped five parliamentary members of their seats.
It has consistently denied petitions by conscientious objectors to military conscription, a jailable offence.
But the bench's conservative leaning may not be enough to help Park, considering the evidence against her, said the two former judges, Kim and Ha.
Park is accused by lawmakers of failing her constitutional duty to uphold the basic principles of free democracy and violating the law by colluding with a friend and former aides. She has been named by prosecutors as a co-conspirator in the corruption case against her friend, but has immunity from prosecution while she is in office.
"Park keeps putting herself ahead of the people, making things complicated," Kim said.
"I believe the judges will make a decision based on their love of the country and conscience. They are also people of the Republic of Korea, breathing the same air as all of us."
Editing by Tony Munroe and Raju Gopalakrishnan